Method for making paperboard for food container

ABSTRACT

A method for making a paperboard includes a first process and a second process, wherein the first process includes steps of making a coating liquid by mixing bio-degradable liquid and primer, arranging the coating liquid in a container, sending the coating liquid to a roller unit by rollers and transporting the coating liquid to a printing unit by the roller unit. The second process includes steps of pre-heating the paperboard and eliminating static electricity from the paperboard, coating the coating liquid on the paperboard by the printing unit, one of rollers of the printing unit coating one or two sides of the paperboard with the coating liquid, pressing the paperboard to a desired shape and drying the paperboard.

FIELD OF THE INVENTION

The present invention relates to a method for making paperboard for food containers and the paperboard is coated with a coating which is composed of biodegradable liquid and primer.

BACKGROUND OF THE INVENTION

A conventional method for making a paperboard includes a container in which a coating liquid is received which includes coating particles with electronics, a first roller rotatably located in the container and merged in the coating liquid, a power supply which applies a voltage to the first roller, a second roller rotatably located in the container and merged in the coating liquid, a gap defined between the first and second rollers, and a pressing roller which is rotated relative to the second roller and the paperboard is pressed toward the second roller. The particles are spread due to the electric power within the gap and attached to the paperboard. However, the thickness of the coating liquid on the paperboard is too thick because the first and second rollers have to be merged in the coating liquid. The thick coating increases the manufacturing cost and reduces the quality of the paperboard.

The present invention intends to provide a method for making the paperboard for food containers wherein the bio-degradable liquid is coated on one or two sides of the paperboard by a satisfied thickness.

SUMMARY OF THE INVENTION

The present invention relates to a method for making a paperboard and the method comprises a step of making a coating liquid by mixing bio-degradable liquid and primer with a ratio of 9:1; a step of arranging the coating liquid in a container and sending the coating liquid to a roller unit by rollers; a step of transporting the coating liquid to a printing unit by the roller unit; a step of pre-heating the paperboard and eliminating static electricity from the paperboard; a step of coating the coating liquid on the paperboard by the printing unit, one of rollers of the printing unit coating one or two sides of the paperboard with the coating liquid, and a step of scrolling the paperboard to be a paper roll.

The primary object of the present invention is to provide a method for making paperboard for food containers and the paperboard is coated with a coating liquid which is made by mixing bio-degradable liquid and primer with a ratio of 9:1. The coating liquid is water and grease proof.

The present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart showing the steps of the method of the present invention;

FIG. 2 shows the arrangement of rollers and container for proceeding the method of the present invention;

FIG. 3 is an enlarged cross sectional view to show that the coating liquid is coated on one side of the paperboard, and

FIG. 4 is an enlarged cross sectional view to show that the coating liquid is coated on two sides of the paperboard.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1 to 4, the paperboard of the present invention is coated with a coating liquid which is made by mixing biodegradable liquid and primer with a ratio of 9:1. The primer is made by Polyvinyl Acetate (PVA).

Polymer biodegradable materials can be degraded and decomposed by a polymer photo-degradation, polymer heat-degradation or polymer oxidation method to synthesize the polymer biodegradable materials with polyvinyl acetate (PVA). The polyvinyl acetate (PVA) can be electrolyzed to form polyvinyl alcohol and then synthesized with the polymer biodegradable material to produce liquid or the polymer biodegradable material can be converted into free radicals first, and then combined with another polyvinyl acetate (PVA) monomer to form graft copolymers. The two types of polymer chain segments are connected to form block copolymers. In addition, the polymer biodegradable materials and the polyvinyl acetate (PVA) can be chemically reacted and released after the reaction, so as to complete a synthesis process.

The method for mixing biodegradable material particles and copolymers into a synthesized liquid is that the biodegradable material particles are heated to over 150 degrees and melt, and then copolymers are added and mixed to form a synthesized liquid.

The coating liquid made by the way described above is printed on the surface(s) of the paperboard. The method for coating the coating liquid on the paperboard comprises the following steps:

a step of pre-heating the paperboard “a” from a paper roll 1 and eliminating static electricity from the paperboard “a”;

a step of filling the coating liquid in a container 2;

a step of sending the coating liquid to a roller unit 4 by rollers 3 and to a printing unit 5;

a step of coating the coating liquid on the paperboard “a” by the printing unit, one of the rollers of the printing unit 4 including a smooth surface without any orifice so that the coating liquid can be printed on the paperboard “a” by the roller with a smooth surface without any orifice;

a step of sending the paperboard “a” between two rollers of the printing unit 5 and the paperboard “a” being pressed and driven by the rollers, the coating liquid on the roller with a smooth surface without any orifice being printed on one or two sides of the paperboard “a”;

a step of drying the paperboard “a” by a pressing unit 6 which is located beside the printing unit 5 and the paperboard “a” with the coating liquid is pressed, the paperboard “a” being sent to a drying area 7 and dried such that the coating liquid enters in the fibers of the paperboard “a”, the coating liquid being pressed into a thin layer, and

a step of scrolling the paperboard “a” with the layer of coating liquid into a paper roll 8.

The roller that has a smooth surface of the printing unit 5 can be replaced by a roller with concave or convex surface.

By the method of the present invention, the coating liquid can be quickly and evenly coated on the surface(s) of the paperboard “a” by a thin thickness which is only 0.005 mm compared with the conventional coating layer of 0.25 mm.

Furthermore, the coating liquid is made by mixing bio-degradable liquid and primer with a ratio of 9:1, or the coating liquid is made by mixing the primer and the bio-degradable liquid by a ratio of 9:1. The coating liquid is heated by at least 150 degrees Celsius to fully mix the two components to be the coating liquid. The primer is extendable and adhesive so as to be easily attached to the paperboard and the primer reduces crystallization of the bio-degradable liquid due to change of temperature. Therefore, only a small amount of the bio-degradable material is needed and this effectively reduces the manufacturing cost of the paperboard.

The primer can be bio-degradable copolymers.

The biodegradable material is a polylactic acid (PLA) raw material, which is a starch extracted from plants and produced by going through the processes of fermentation, dehydration, and polymerization. Since the biodegradable material can be decomposed into carbon dioxide and water under compost condition, the biodegradable material is an environmental raw material that causes no environmental pollution. In addition, the bio-degradable material can be a polyethylene terephthalate (PET)/polyester like material or various PET like polymer materials including the Biomax 4024 PET manufactured by U.S. DuPont Group or the degradable Fepol manufactured by Taiwan Far East Textile Co., Ltd.

As shown in FIGS. 3 and 4, the paperboard “a” can be coated on one side or on two sides, the coating liquid forms a even and thin layer “b” on the paperboard “a”.

The paperboard “a” made by the method of the present invention can be degradable after use and generates carbon dioxide and water only after being composed.

While we have shown and described the embodiment in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention. 

1. A method for making a paperboard, comprising: a step of making a coating liquid by mixing bio-degradable liquid and primer with a ratio of 9:1; a step of arranging the coating liquid in a container and sending the coating liquid to a roller unit by rollers; a step of transporting the coating liquid to a printing unit by the roller unit; a step of pre-heating the paperboard and eliminating static electricity from the paperboard; a step of coating the coating liquid on the paperboard by the printing unit, one of rollers of the printing unit coating one or two sides of the paperboard with the coating liquid, and a step of scrolling the paperboard to be a paper roll.
 2. The method as claimed in claim 1, wherein the primer is copolymers which is mixed with the bio-degradable liquid by a ratio of 9:1, the coating liquid is heated by at least 150 degrees Celsius.
 3. The method as claimed in claim 1, wherein the primer is copolymers which are mixed with the bio-degradable liquid by a ratio of 1:9, the coating liquid is heated by at least 150 degrees Celsius.
 4. The method as claimed in claim 1, wherein the bio-degradable liquid is a Polylactic Acid (PLA).
 5. The method as claimed in claim 1, wherein the bio-degradable liquid is made by a material similar to PET.
 6. The method as claimed in claim 1, wherein the bio-degradable liquid is made by a material similar to PET which is Biomax 4024 PET by DU PONT.
 7. The method as claimed in claim 1, wherein the bio-degradable liquid is made by a material similar to PET which is Fepol by Far-Eastern Textile Ltd.
 8. The method as claimed in claim 1, wherein the primer is made by Polyvinyl Acetate (PVA).
 9. The method as claimed in claim 1, wherein the primer is made by Vinyl Acetate Resin. 